Generic spring carriers are usually used for plant construction for the resilient support of pipes or of components such as, for example, valves. This being, generic spring carriers make possible the resilient carrying of a load up to a nominal load that is defined by the construction of the respective spring carrier, in particular by the spring used therein. Spring carriers with different nominal loads exist for different applications; typically, the nominal loads of generic spring carriers are situated between 0.5 kN and 500 kN. Depending on the application, generic spring carriers can be designed as spring hangers or as spring supports. A spring support is designed to be mounted on a carrier, the spring support having a carrier element that forms the upper end of the spring support and on which a load such as, for example, a tube can be resiliently supported. A spring hanger is designed to be hung to a carrier or to be laid onto a carrier, the spring hanger having a carrier element that forms the lower end of the spring hanger, whereby a load such as, for example a tube, can be resiliently suspended to the carrier element.
Generic spring carriers comprise a casing tube, the cylinder axis of which extends in a longitudinal direction. A base plate, a spring plate and a spring are placed in the casing tube in the longitudinal direction between an upper boundary element and a lower boundary element, the spring being placed between the spring plate and the base plate and applying a spring force to the base plate and the spring plate. The spring plate is connected to a carrier element of the spring carrier. The boundary elements are of significant importance since they limit the longitudinal displacement path of the spring plate inside the casing tube. In unloaded condition, the upper boundary element absorbs the spring force acting onto the spring plate and the lower boundary element the spring force acting onto the base plate. In loaded condition, a load is applied to the spring plate by the carrier element so that the spring is compressed in the longitudinal direction and the spring plate is no longer applied to the upper boundary element. In loaded condition, the lower boundary element also absorbs the force of the spring acting onto the base plate, this force being composed of the spring force in unloaded condition and of the weight force of the load.
Usually, the boundary elements are often produced by bending the casing tube. However, other possibilities are also known for the implementation of the boundary elements, for example the welding of boundary elements to the inner circumference of the tube casing, for example the welding of a flange to the outer surface of the casing tube and the subsequent screwing of a boundary plate to the flange for constituting a boundary element. This being, usually the upper boundary element is first produced by bending the casing tube, whereupon the spring plate, the spring and the base plate are inserted into the casing tube by compressing the spring, whereupon the lower boundary element is then produced in a further bending step. A reliable fixing of the spring plate, of the spring and of the base plate in the casing tube can thus be achieved. Spring carriers that should be appropriate for the use under slightly corrosive conditions can be protected against corrosion by a paint coat or by electro galvanizing before and/or after the bending steps.
However, the production of spring carriers for highly corrosive environments is problematic. For such spring carriers, the casing tube has imperatively to be provided with a sufficiently thick protective layer against corrosion, which usually takes place through hot-dip galvanizing. A bending of the casing tube after having applied an appropriately thick protective layer is no longer possible since this would result in a destruction of the protective layer in the bending area. However, at the same time the hot-dip galvanizing of the casing tube is no longer possible when the spring is in the casing tube since the spring properties of the spring would be considerably impaired by the high temperatures of hot-dip galvanizing, if not even destroyed. For this reason, in case of traditional spring carriers for highly corrosive environments, the casing tube usually comprises a tube section and a plate section welded at the lower end of the pipe section, an upper boundary element formed by bending the tube section being placed at the upper end of the tube section. In such spring carriers, the base plate is not placed inside the casing tube but is screwed from below to the plate section of the casing tube. There is no problem to hot-dip galvanize the casing tube, whereupon the spring plate and the spring can be inserted from below into the casing tube and the base plate can be screwed by compressing the spring against the plate section.
A spring carrier with a sufficiently thick protective layer against corrosion can certainly be produced but such a construction gives rise to crucial disadvantages. So, for example, the screws with which the base plate is screwed against the plate section of the casing tube are necessarily in the longitudinal direction and thus in direction of the force that the spring exerts onto the base plate and that is composed of the spring force in unloaded condition of the spring carrier as well as of the weight force of the load resiliently supported by the spring carrier. This can easily result to an overloading of the screws and to a damaging of the spring carrier. Moreover, the production of such a spring carrier is costly since first the welding of a plate section to a tube section for producing the casing tube and then a costly screwing of the base plate to the plate section are necessary. In EP 0 184 404 A1, for example, a spring carrier is disclosed that has a casing tube in which an upper plate and a lower plate are placed as components separated from the casing tube. The spring carrier can be suspended to the upper plate; a coil spring by which a load can be resiliently carried is supported on the lower plate. The upper plate as well as the lower plate is respectively supported on projections provided in the casing tube, the upper plate being twist-secured by pins that are inserted laterally into the plate through feedthroughs of the casing tube. In U.S. Pat. No. 2,417,154 A, a spring carrier is disclosed that has a casing tube that is closed at one end by an end cap designed as a separate component. Springs by which a load can be resiliently carried are supported on the end cap. The end cap has several projections spaced from each other over the circumference and is supported in the casing tube by these projections in that these projections of the end cap are supported on projections that are provided in the casing tube. Furthermore, guiding ribs that bear on the projections of the end cap and that prevent a twisting of the end cap and thus a loosening of the end cap from the casing tube are provided on the casing tube. A spring carrier that is designed as a spring support is disclosed in FR 2 365 727 A1. A spring carrier that comprises a casing tube that is closed at one end by a base plate to which a spiral coil is supported for bearing a load is disclosed in U.S. Pat. No. 4,176,815 A. The base plate is designed as a separate component and is supported in the casing tube by means of a bayonet lock. A spring carrier that comprises a casing tube is disclosed in GB 2 029 928 A, casing tube in which a lower pressure ring and an upper pressure ring are placed as separate components, Woodruff keys being placed between the pressure rings. The lower pressure ring is supported on projections provided in the casing tube and the upper pressure ring is supported in the casing tube, the casing tube being pressed-in above the pressure ring by maintaining a pressure onto the upper pressure ring. A spring carrier that has a casing tube is disclosed in US re. 22,980 E, an upper plate and a lower plate being placed in the casing tube, the upper plate as well as the lower plate being welded with the casing tube.